This application claims the priority of German patent document no. 10 2004 009 467.5, filed Feb. 27, 2004, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a control system for a vehicle.
German patent document DE 100 32 179 A1 discloses such a control system, which operates with an electronically actuated drive train that comprises at least a steering system, a brake system and a drive train of the vehicle. The system also includes an input level with the devices for inputting continuous values predefined by a driver and for converting the predefined values into setpoint value signals. A coordination level converts the setpoint value signals into actuation signals which are implemented by actuators of the drive train. In other words, the control system has a control device which generates output control signals for actuating the drive train, in response to an input movement vector. In order to transmit the control signals the control device is coupled to the drive train which then processes the control signals in order to implement the driver's request, referred to as a “drive-by-wire system” or an “X-by-wire system”.
German patent document DE 100 46 832 A1 discloses a further vehicle control system which is equipped with an electronically actuated drive train. Vehicle data relating to vehicle movement dynamics, time, vehicle position, driver-end activation signals and actuation signals for the drive train which are generated by a control device are stored in a memory device.
Such a control system permits an improved analysis of accidents.
One object of the present invention is to provide an improved control system of the latter type which achieves rapid response and increased driving comfort.
This and other objects and advantages are achieved by the vehicle control system according to the invention, which is directed to a vehicle having an electronically actuated drive train, a coordination level, and an execution level which is subordinate to the coordination level. According to the invention, an axle electronic module which is designed to activate at least one brake actuator assigned to the chassis, is arranged near a steerable vehicle axle. The axle electronic module is connected here to axle actuators assigned both to the coordination level and to the vehicle axle, and receives setpoint values generated by the coordination level from driver's requests in order to determine actuation signals that actuate the respective axle actuator.
The control system according to the invention has at least two control levels. Specifically the coordination level (which is assigned to a control device and in which setpoint values are generated from state variables of the vehicle and from driver's requests) generates actuation signals for actuating actuators in response to the setpoint values. The execution level, which is subordinate to the coordination level and is assigned to the axle electronic module, has actuators for executing the actuation signals. It is significant that the axle electronic module i) is designed to activate at least one brake actuator assigned to the vehicle axle; ii) is arranged in the region of the steerable vehicle axle; iii) is connected to the coordination level in order to transmit setpoint values; iv) is designed to determine actuation signals for actuating the respective axle actuator from the setpoint values; and v) connected to an electronically actuated steering system for transmitting the actuation signals.
This means, that in contrast to previous control systems, the abovementioned axle-specific elements or systems are now controlled by the axle electronic module, while further actuators are actuated in a conventional manner with the control signals which are generated in the coordination level. The axle can also be checked functionally by actuating the sensors, actuators and the axle electronic module on or near the steerable axle.
The invention provides the advantage of integrating or bundling all the control processes for axle-specific actuators in the axle electronic module, and to that extent separating them from the conventional control system. The axle electronic module (which is arranged in the region of the steerable vehicle axle) is located in the direct vicinity of the axle actuators, so that the line paths between the axle actuators and the axle electronic module are significantly shortened in comparison with the previous embodiment. As a result, the cables required and the control times can thus also be reduced. In this manner, interconnection of the axle actuators to the axle electronic module is simplified, achieving advantages in cabling and of fabrication. At the same time, such an arrangement makes it possible to integrate at least part of a coordinating software package for actuating axle-specific functions (for example braking and/or steering) into the axle electronic module (and thus into the execution level).
Local arrangement of the sensors, actuators and axle electronic modules eliminates the variance of the line, and reduces the lengths of the lines and variants. In addition, it avoids installations which are defective from the very beginning.
The steering system can expediently be embodied as a steer-by-wire steering system and operate with a steering algorithm that can be modified as a function of the actuation signals. As a result, the electronically actuated steering system and brakes can be advantageously interconnected with one another, and both can be controlled as a function of acquired state variables (such as, for example, a lateral acceleration when cornering) and as a function of predefinable driver's requests.
In the coordination level, setpoint values for the brakes and for the steering system are generated from the driver's requests and the acquired state variables, and are transmitted (for example via a CAN bus system) to the local axle electronic system which transforms electrical actuation signals from the latter for the brakes and for the steering system. Predictive algorithms of the coordination level permit early detection of cornering in this context and adjust both the steering system and the brakes in an optimum way by means of corresponding actuation signals to the respective actuators. The vehicle movement dynamic state variables, mentioned previously, are sensed here by sensors and transferred to the axle electronic module.
The axle electronic module is expediently designed to control the at least one brake actuator and/or the controllable steering system and to take into account the “Kamm's Circle” (described hereinafter). That is, each tire can transmit only a certain maximum acceleration force and a certain maximum lateral guiding force to the road. If the tire is to transmit a maximum lateral guiding force, neither acceleration nor deceleration can occur; on the other hand, when there is a desired maximum acceleration force of the tire the tire cannot transmit any lateral guiding force at all to the road. When both forces occur, they maintain a relationship with each another that can be represented figuratively by means of the Kamm's Circle. In this context, the lateral guiding force is applied orthogonally with respect to the acceleration force and forms a force parallelogram of the two forces. The resulting force must not be greater than the radius of the Kamm's Circle here if it is desired to travel through the bend without danger. If the resulting force is greater than the radius of the Kamm's Circle, the centrifugal forces can become too large, so that the vehicle moves out of the curve.
The axle electronic module can expediently comprise electronics, software, and/or local control circuits for at least one of the following functions: braking, steering, additional drives, pitching and/or rolling, and controlling of a ride level. As a result, a large number of axle-specific or chassis-specific electronic and/or software components and/or control circuits are integrated into the axle electronic module and thus permit a rapid response to changing data, such as driver's requests and/or state variables of the vehicle. In addition, predictive algorithms, which permit optimum adjustment with respect to consumption and drive comfort, may be programmed in the coordinating software.
According to one advantageous embodiment of the invention, the electronics, software and/or local control circuit for the brake function controls at least one element from the following list: brake pressure, local ABS, ABS signal sensing and processing, active wear adjustment for a vehicle brake, and sensing of brake lining wear. This list is intended to show that the electronics, software, and/or local control circuit which controls the brake function has a plurality of subfunctions, a few of which have been mentioned above. The axle electronic module can thus sense and/or control a large number of axle-specific characteristic values. Further elements which can be controlled by the axle electronic module are, for example, a tire management system which calculates a coefficient of friction between the underlying surface and tires, a tire pressure sensor and further axle-related actuators.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.